Lycopene

Lycopene, found primarily in tomatoes, is a member of the carotenoid family—which includes beta-carotene and similar compounds found naturally in food—and has potent antioxidant capabilities.

A study conducted by Harvard researchers examined the relationship between carotenoids and the risk of prostate cancer.1 Of the carotenoids studied, only lycopene was clearly linked to protection. The men who had the greatest amounts of lycopene in their diet (6.5 mg per day or more) showed a 21% decreased risk of prostate cancer compared with those eating the least. This report suggests that lycopene may be an important tool in the prevention of prostate cancer. This study also reported that those who ate more than ten servings per week of tomato-based foods had a 35% decreased risk of prostate cancer compared with those eating less than 1.5 weekly servings. When the researchers looked at only advanced prostate cancer, the high lycopene eaters had an 86% decreased risk (although this did not reach statistical significance due to the small number of cases).

Contrary to popular opinion, research suggests that there is no preferential concentration of lycopene in prostate tissue.2 Although prostate cancer patients have been reported to have low levels of lycopene in the blood,3 and lycopene appears to be a potent inhibitor of human cancer cells in test-tubes,4 evidence is conflicting concerning whether an increased intake of tomato products is protective against prostate cancer. Some studies, like the one discussed above, have reported that high consumption of tomatoes and tomato products reduces risk of prostate cancer.5 6 Other studies, however, are inconclusive,7 and some have found no protective association.8 9 10 11 12

There is some evidence that lycopene may be helpful in the treatment of prostate cancer. In a preliminary trial, 26 men with prostate cancer were randomly assigned to receive lycopene (15 mg twice a day) or no lycopene for three weeks before undergoing prostate surgery. Prostate tissue was then obtained during surgery and examined. Compared with the unsupplemented men, those receiving lycopene were found to have significantly less aggressive growth of cancer cells.13 In addition, a case report has been published of a 62-year-old man with advanced prostate cancer who experienced a regression of his tumor after starting 10 mg of lycopene per day and 300 mg of saw palmetto three times per day. As saw palmetto has not been previously associated with improvements in prostate cancer, the authors of the report attributed the response to the lycopene.14 Long-term controlled studies are needed to confirm these promising initial reports.

There is no evidence that tomato intake has any effect on benign prostatic hyperplasia (BPH).

Another study found that for the 25% of people with the greatest tomato intake, the risk for cancers of the gastrointestinal tract was 30–60% lower, compared with those who ate fewer tomatoes. These reduced risks were statistically significant.15 A study of women found that the 75% who ate the least amount of tomatoes had between 3.5 and 4.7 times the risk for pre-cancerous changes of the cervix (cervical intraepithelial neoplasia).16 Other researchers have also reported evidence suggesting that high dietary lycopene may be linked to protection from cervical dysplasia.17 While preliminary evidence also links dietary lycopene with protection from breast cancer,18 another study did not find this link.19

In a review of 72 studies,20 one researcher reported 57 associations between tomato intake or blood lycopene levels and decreased risk of cancer. Of these associations, 35 were statistically significant. The benefit was strongest for prostate, lung, and stomach cancers, although protective associations were also found for cancers of the pancreas, colon, rectum, esophagus, oral cavity, breast, and cervix. Because the data were from observational studies, a cause-and-effect relationship cannot be firmly established. However, the consistently lower risk of cancer associated with higher consumption of lycopene-containing tomatoes, provides a strong foundation for further research on lycopene.

In Europe, researchers have found a statistically significant association between high dietary lycopene and a 48% lower risk of heart disease.21 Lycopene supplementation has also boosted immune function in the elderly. In that trial, 15 mg of lycopene per day increased natural killer cell activity by 28% in 12 weeks.22

Where is lycopene found?

Tomatoes and tomato-containing foods are high in lycopene. In the Harvard study, the only tomato-based food that did not correlate with protection was tomato juice. In an unblinded, controlled trial, lycopene supplementation, but not tomato juice, effectively increased the body’s lycopene stores.23 These studies suggest that the lycopene present in tomato juice is poorly absorbed. However, other research indicates that significant amounts of lycopene from tomato juice can, in fact, be absorbed.24 Other foods that contain lycopene include watermelon, pink grapefruit, and guava.

Lycopene has been used in connection with the following conditions (refer to the individual health concern for complete information)